Concept cars give automotive designers a chance to let their imaginations run wild, often with outlandish results. But even by that measure, BMW has come up with something as strange as it is innovative — a shape-shifting car covered with fabric. Instead of steel, aluminum or even carbon fiber, the Gina has a body of seamless fabric stretched over a movable metal frame that allows the driver to change its shape at will. The car — which actually runs and drives — is a styling design headed straight for the BMW Museum in Munich and so it will never see production, but building a practical car wasn’t the point.